Unfortunately it takes more than a casual interest in chemicals to be certain, without actually doing some tests. A few little notes to help:
1) If the product gets diluted with water before use, chances are it is water based.
2) If the product is clear and smells of hydrocarbons (you need to be able to discern between solvent for this to help!), it is probably a solvent base.
3) If the product is a milky emulsion or paste, it will have water in it but you will not be able to be certain if it is oil-in-water or water-in-oil.
4) If a product separates into giving an oily layer, the product will likely contain water but is unfortunately lacking in stability. This behaviour would often not be tolerated if selling to large consumer applications. Unfortunately, detailing products are not big enough to force that such instability is corrected - detailers tend to just accept it rather than refuse and force the manufacturer to fix it.