I naturally have big hands so, I don’t have much problem reaching, but I do know that in order to hold that stretch you need dexterity and strength. Here’s a technique that’s helped me do both and not only does it give you the dexterity and strength (over time of course like any exercise would) it does it for each individual finger, giving you the ability to have more finger control.
Starting on the 1st fret with your index finger, pick your note: 1 & a 2 & a 3 & a 4. It’s imperative that you do this very slowly.Now while still holding your index finger on the first, take your middle and hold the 2nd, never releasing the index from the first: 1 & a 2 & a 3 & a 4. Ring finger to 3rd, again not releasing the 1st or 2nd from their frets: 1 & a 2 & a 3 & a 4… and the pinky on the 4th, also never releasing the other fingers: 1 & a 2 & a 3 & a 4.
Now this is probably where you’re like can I stop now? but no, you must do it for each string. Now, remember your fingers are still in line on the 6th string (The low E) now without releasing any but your index, place that on the 1st fret on the 5th string (The A): 1 & a 2 & a 3 & a 4. Never releasing, the index from the 1st fretted on the A and having your ring and pinky still on the E, take your middle finger and place it on the 2nd of the A: 1 & a 2 & a 3 & a 4. Notice how you never release your fingers unless you’re moving to the next string? Do this for every string as long as you can stand, everyday before playing guitar. With in a couple weeks you will notice strength and after a month or so finger movement will seem more fluent.
But most of all!! Have fun. ;)