Although Geralt does not need to drink to quench his thirst during the game, he is able to derive some benefit from non-alcoholic beverages (listed below) if he has no healing potions left. He can also indulge in some recreational drinking, but that requires alcoholic beverages and does not give any regeneration bonuses. There is also hard liquor, which is needed for potion bases.
Drink provides a slightly accelerated endurance regeneration which lasts for 9 game minutes. (see notes for restrictions)
The price of an item is based on the perceived difficulty to acquiring it, not the amount of vitality or endurance the item restores. More precisely, all food and drink seems to increase vitality regeneration for 9 minutes, but some food items are more expensive than others.
Selling price is always one fifth (20%) of the buying price. Thus an item costing 5 will sell for 1. Bottled Water costs 3, but because the selling price is less than 1, no one will buy it!
When consuming an item for the purpose of increasing regeneration, it is important to avoid using the same type of item if you want to gain several bonuses at once. For example, eating two blueberries will only show one vitality regeneration effect in the HUD, but eating a blueberry and a loaf of bread would show two.
In the Enhanced edition, you must eat/drink items with different prices to get several regeneration bonuses. If you eat food/drink that costs the same, the countdown will merely reset. For example, if one eats a blueberry (sells for 1 oren) and bread (also 1 oren), you will not get a second vitality regeneration bonus, but if you eat a blueberry (1 ores) and a watermelon (2 orens), you will get 2 vitality regeneration bonuses.
By this method, you can have a maximum of 5 vitality regeneration bonuses (1-5 orens).