Dehydration recovery time depends on how dehydrated you are.
If you are severely dehydrated, it’s likely that you will be hospitalized and put on intravenous hydration for up to 24 hours, or until you’re able to drink oral rehydration fluids yourself. When you’re severely dehydrated, you need to put back a LOT of fluid, and it needs to be balanced with the nutrients that your body usually contains.
If you were to suddenly put a lot of water back into your body after being severely dehydrated, it might cause your body to go into a form of shock, so you need to pace yourself.
At less severe dehydration levels that are still serious, it’s possible that you’ll be only drinking oral rehydration fluids. CDC guidelines for those suffering from dehydration through Cholera recommend drinking up to 1 liter of ORS fluid per hour for an adult, and children 20ml / kg of body weight. 
How long does dehydration last?
If you don’t treat dehydration by drinking water and in some cases taking on electrolytes in the right quantities, your dehydration will last indefinitely. If it progresses for long enough, you can die from dehydration. Most of us know this - you can go weeks without food, but only days without water.
We made Hydrant to be an effective way to rehydrate quickly. Because it’s in a convenient powder pack, wherever you are in need of hydration, you can mix it in with some water and begin getting hydrated as soon as possible.
 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC419333/ (This is a meta-analysis of randomized control studies comparing oral rehydration against intravenous rehydration. Randomized control trials are very high quality studies, and meta-analyses look at many of them to draw conclusions.)
 https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0082773/ (This link is a long form article titled: "Principles and protocols for intravenous fluid therapy". It's an in depth clinical guide for medical professionals.)
 https://www.cdc.gov/cholera/treatment/rehydration-therapy.html (CDC page on Oral Rehydration)