If you want to cheat for a fee, then you can through the Seosprint website, but if it's fast and free, then try the applications, you can subscribe to people yourself and you will be awarded points for this, and invite subscribers for these points.
To quickly gain subscribers to your YouTube channel, you need to make a good video and description for it and make a button at the end of the video so that people subscribe.
Mostly subscribe to well-made channels with quality videos.
There are many cheat sites, but it is better not to use them, since this is fraught with at least the fact that subscribers are unsubscribed, but some sites offer a service with which you can attract LIVE subscribers, for example, a social network Kaleostra, more in the video
How to get subscribers to your YouTube channel:
create good videos with original captions;
write on thematic forums with a link to the channel;
recruit through social networks (kaleostra, for example) or other resources;
mutual subscription to the channel (will also bring a certain number of subscribers).
Create and post an interesting video that will attract users and will be popular and in demand on this resource. Place in your video special links to your other video and offers to subscribe to your channel.
Just make high-quality videos. Write an original title. Make a beautiful channel design. Write as many tags as possible on each video. I gained 20 subscribers in 210 days.