However, "don't apply for jobs you don't really care about" is a very 50/50 advice. Right now I have zero money reserves. If I somehow got fired tomorrow, I'll be in the red even after 2 days of unemployment. So sometimes you have to make a hard choice.
That being said, it's good to be open about this after you get your act together months later and decide what to do with your current employer, during a lunch for example.
CLARIFICATION on the leverage remark: it's my opinion that 99% of the time leveraging an offer from another company that wants to give you more money, to make your old company give you more money, is a huge mistake. Most businessmen HATE being strong-armed, or, to use a milder language, hate being shown that their employees have power over them, and this makes them hate you even if they very much need you in a business sense. They end up actively looking for a way to get rid of you, even if it costs them more money and/or stress in the long-term. I've witnessed it.
SOURCE: 4 of my stupider younger acquantainces from 7-12 years in the past. And an observation from my first job. After I "strong-armed" my first employer to double my then pretty measly salary, he went on a hunt to replace me (even though it took him around a year to really do it), but I was smart enough to detect the signs and resigned long before he had the chance. No regrets.