Insert line break using SKLabelNode in SpriteKit

I dont think you can, here is a "hack" way to do it

SKNode *nerdText = [SKNode node]; 
SKLabelNode *a = [SKLabelNode labelNodeWithFontNamed:@"Arial"];
a.fontSize = 16;
a.fontColor = [SKColor yellowColor];
SKLabelNode *b = [SKLabelNode labelNodeWithFontNamed:@"Arial"];
b.fontSize = 16;
b.fontColor = [SKColor yellowColor];
NSString *st1 = @"Line 1";
NSString *st2 = @"Line 2";
b.position = CGPointMake(b.position.x, b.position.y - 20);
a.text = st1;
b.text = st2;
[nerdText addChild:a];
[nerdText addChild:b];
nerdText.position = CGPointMake(150.0, 250.0);
[self addChild:nerdText];

I had the same problem. I created a drop-in replacement for SKLabelNode called DSMultilineLabelNode that supports word wrap, line breaks, etc. The underlying implementation draws the string into a graphics context and then applies that to a texture on an SKSpriteNode.

It's available on GitHub at:

https://github.com/downrightsimple/DSMultilineLabelNode

 static func multipleLineText(labelInPut: SKLabelNode) -> SKLabelNode {
        let subStrings:[String] = labelInPut.text!.componentsSeparatedByString("\n")
        var labelOutPut = SKLabelNode()
        var subStringNumber:Int = 0
        for subString in subStrings {
            let labelTemp = SKLabelNode(fontNamed: labelInPut.fontName)
            labelTemp.text = subString
            labelTemp.fontColor = labelInPut.fontColor
            labelTemp.fontSize = labelInPut.fontSize
            labelTemp.position = labelInPut.position
            labelTemp.horizontalAlignmentMode = labelInPut.horizontalAlignmentMode
            labelTemp.verticalAlignmentMode = labelInPut.verticalAlignmentMode
            let y:CGFloat = CGFloat(subStringNumber) * labelInPut.fontSize
            print("y is \(y)")
            if subStringNumber == 0 {
                labelOutPut = labelTemp
                subStringNumber++
            } else {
                labelTemp.position = CGPoint(x: 0, y: -y)
                labelOutPut.addChild(labelTemp)
                subStringNumber++
            }
        }
        return labelOutPut
    }