Pretty much everyone in class soon switched to using Everclear.
I stick with high-concentration rubbing alcohol, or I just buy Everclear from the liquor store. Everclear is food-grade, though I never have tried to actually consume it. Wisconsin at least used to sell it up to 98% pure (196 proof IIRC) though I believe many other states only allow 180 or 190 proof.
If you can get straight grain alcohol like that it might be your best bet as far as purity is concerned.
In California the strongest that can be legally sold for beverage purposes is 151 proof, or only about 75% alcohol (leaving about 25% water.)
Pure unpoisoned food grade alcohol is certainly best, but is also very expensive.
It is expensive because it is taxed a lot at various stages.
Most of the cost of alcohol is taxes, some taxes in creating it, and taxes federal and state selling it. The cost of "cheap" beverage alcohol is typically from 50% to 90+% taxes depending on additional state taxes. However additional taxes also exist for the manufacturer.
For example here is industrial 190 proof alcohol prices:
http://www.ethanolmarket.com/industrialethanol.html
Ethanol prices per gallon are extremely cheap. It is made primarily from corn in the USA. Denatured fuel ethanol being around $1.50 a gallon ($1.60 is says as I write this.)
Almost the same process is used to create cheap beverage alcohol, but they don't add the poison, and they must pay more to process it under the proper licenses.
Now compare that cost to what retail food grade 190 proof costs.
You certainly are not likely to find an entire gallon of 190 proof even sold.
Consider your typical 750ml alcohol bottle. 25.36 US fluid ounces is 750ml.
There is 128 fluid ounces in a gallon.
It would take over 5 typical 750ml bottles to make one gallon.
Yet each one of those 750ml bottles is going to cost several times what an entire gallon of the poisoned stuff costs.
The percentage of cost increase is mind boggling. Thousands of percent for the same product without poison added.
If beverage alcohol was unrestricted most of the cost of the cheap grain alcohol would be stemming from bottling and shipping costs (and marketing). It would be similar in price to soda.
The cost is artificially high to reduce consumption, and to fill the coffers of government.
I have run into this issue making perfumes and food/flavoring extracts (where the alcohol is evaporated off and is not contained in the final product) which require the beverage stuff.
190+proof alcohol and diethyl ether are the primary food quality solvents used industrially to produce food quality products.
Diethyl ether works even better as food safe solvent (very low boiling point makes it easy to remove, and it is a strong solvent) that does not leave toxic byproducts, but it is restricted because it is also used to manufacture drugs.
(Of course I don't do any of that stuff anymore because I could just see some overzealous prosecutor or cop claiming it was a meth lab or something crazy and a jury not knowing any different. Lab equipment is too much of a liability to keep as a result.)