Drinks
Electrolyte replacement

Where hyponatremia is not concerned, assume 3 liters is not a problem.
A good choice is to use the balanced fuel supply for the rides lasting more than an hour, and use water for anything less than an hour. Drinks with a mixture of carbohydrate, protein and electrolytes are more preferable than ordinary ones with carbohydrates only.

It is also cheaper and much more effective than most branded drinks. Available easily too, they can be purchased easily from local shops, and online stores too. However, the local ones are cheaper than their online counterparts.

Food
Food for a 20 mile ride

Usually, a 20 mile ride on a “mountain terrain bike” or MTB takes around 1 hour 25 minutes to 1 hour 30 minutes.

Many of us cycle not only to build fitness, but to reduce our bodyweight also.
For these, we need to gradually increase the duration of the rides, if currently it is 1 day per week, it needs to be raised to 3 to 4 days per week.

There is no need to buy expensive foods like the energy bars, just rely on the regular ones like bread, bananas, pasta, etc. which have a balanced carbohydrates and proteins and vitamins.

And make it a point to drink lots of fluids during your ride, so that you do not get dehydrated.

Food for energy

A good time-tested food is brown-bread banana with honey sandwich.
Have a light meal, so that you do not feel heavy during riding.
Have oats or brown breads, the slow carbohydrates which gives you energy for a long and sustained period.

Take your food 2 hours before riding, as it is very hard to digest while riding.