The most commonly used solvent is water. Ethanol is also a major one: https://www.worldofmolecules.com/solvents/
Or do we need to restart that program to ban all use of the horrible dihydrogen oxide solvent that pollutes over 70% of the surface of the world? ;)
Caffeine LD50: 150-200 mg/kg (according to Wikipedia).
Maximum allowed amount of methylene chloride in beverages, the dreadful paint thinner, according to the link above: 10 ppm, or about 2 mg per cup.
Methylene chloride LD50: 1.25 g/kg (again, according to Wikipedia).
I.e., you will literally die of caffeine poisoning long before the paint thinner gets you.